Process for making colloidal silica



Patented Aug. 16, 1932 "rum-S EN 'ms rERcY-w. PORTER; or WILMINGTON; nivn'nussnnr. or LOSANGELEQ, CALIFORNIA .1

ramm ng. i

A f rnocnss non m sizmefconnornnnsinrcn This invention relates to alprocess'formaking colloidal silica,'otherwise known as silica gel',bya new and novel method; I P

Colloidalsilica or silica gel has been made for many years and its adsorptive properties are wellknown. i V j Heretofore the common method'of producingcolloidal silica or silica gel includes the addition of'a solution ofsodium silicate to asolution ofhydrochloric acid; Great care must be exercised in uniting these solutions, a vigorous stirr ng being necessary at the moment ofmixing to prevent coagulation. A

liquid solution of colloidal silicic acid results,*which upon standing, sets to a solid mass of firm jelly. Afterwashing and drying, thisjelly becomes a hard porous glassy granular substance which is essentially silica 310 containing from to a water together with a small amount ofsodium chloride which is impracticable to wash out. The colloidal silica or silica gel produced as above described has numerous ultra-microscopic 0:41 o. csper gramof silica. v

-The-presence of lkali metal salts in colloidal silica causesian ecceleration ofthe cryse pores which have an internal volume of about i tallization ofltheisilica upon heating. The

absence of alkali metal salts renders colloidal silica resistant to a greater amount of heat, a valualble factorin re-activating the colloidal silica aftjer having beenusedsto adsorb imf purities from petroleumproductsz 1 i'L Iheprimary object-of this invention is to ,provide a process for producing a colloidal silica on silica gelwhich ihasv'aimore fully ideyelope di pore structure and (consequently possesses-greater 'adsorptive powers thanthat producedby the method described above;

further'object is to providea process "which produces a colloidal silica free from tion of sodium silicate; a solid solution of 60 metal alkali salts, such as sodium chloride, inconsequence "of which it has the property of resisting a greater amount of heat, With out injury, and may be re activated for re pea-ted use oftener than products of present methods,

ilfil this invention,-instead solumeta-silicic acid is ,treatedwith a solution of hydrochloric acid. r 'llhi saimaterial' I :turnishedin the mineral 'laumontite, a dry natural silicate, having the 'composition of GaO, A1 0 4bi0 ,"4-H' O.i 'lhat this mineral isa solid: solution of metasilicic acid is demonstrated as follows. Laumontite composition may belregarded as being UaO, Al5O 4LH SiU iff the water and silica are combined. Froni'a large number of tests it has been 'proVen-that the only action of the-hydrochloric acid isto combine" Calculating on thebasis of one pound of pure laumontite requires a volume of hydrochloric acid solution of 4800 ml. having a specific gravity of 1.0286 with 'a concentration of iiGlgas 5.70% yielding 0.820]? a pound of ortho-silicicacid or 0.5101 a. pound ofdry colloidal silica a Si0 lhese quantities very closely agree withtests, a a i "lhe mineral laumontite. was selected from a number 'of otherminerals on account of its high percentage of silica, (the absence 'of alkali metalsalts, the absence of heavy metal salts, the low per cent of HClgas required to liberate the ortho-silicic acid and the discovery of a zcommercialdeposit of rockcarrying up to of laumontite.

It has been known for many years that from laumontite a jelly of silicic acidicould be obtained by using a hot concentrated so- The method of procedure is as follows:

' Start with a Vessel of unit size, say one liter.

Use 900 ml. of acid solutionwhich from the above reaction would require 144.54 ml. of

commercial hydrochloric acid Be. specific gravity 1116 with a concentration of 31.45% of HCl gas and 755.46 ml. water. A small excess of acid is used to take care of soluble impurities. For-example useZ150 ml. I-ICl B. 20 and750 ml. Water.

andllaumontiteais. ground 130200 mesh fine ness and mixed with'the acid solution;

V "2N9 .particulanskill isrequiredzm.mixing. other thanpaslight stirnin'gto insure the dry powder to bethoroughly moistened. There is no dangero'f coagulation of. the silicic, acid.-

No. application; of .heatiis;necessaryflalthough i it has been fcund that'by heating the acid to suflicient to; be noticedwhenpthe h d about. 403,9..increases the -..oiit-p,ut;so w iat. The final, mixture to. which no heat asb ln applied, developsa slight. r se intempe ture placedon theside of the vessel. flhei lso uble portionioft epowder is allowed to .tle,-=th.e I liquid loses i s e c ss, he t. i w ew minutes; and becomes opa1esc ent.-. Th reac-v tion,isjn wacomplet iand,the supernat nt liquidicolloidal. solutionis decanted into a su ic ent numbe ofraysso thet th l qu d is ahoutono nch deep and. al wedrt t nd 'This' colloidal solution will setjto; a ,fi ,rm solid mass of jelly 8 to 24 hours depending P QW 4 5 th tee age; of i ite in the rock has been calculated. The for mation of this jelly, which; is orthmsilicic acid, do'es not depend. upon evaporation, in

fa'ctit has been observed that theje'lly-starts 1 to format the bottom of the vessel and grades ally proceeds upwaixl. -The jelly is' not dis turbed, but isjleft in" the trays and placed in the :direct rays of the sun in 1a location open to the natural breezes 4 to dry.

7 The best quality of'colloidal-silica is'produced' by slow drying'of the jelly." i If possible this drying is done in *an atmosphere of=-low relative humidity such as occurs in the arid regions of "Southern California. If such an atmosphereEis not available a drying room may be prepared to simulate suchatmosphere; The jellyis dried'until the-calcium andaluminum chlorides have "crystallized, which requires from3to 6 days. The crystallization of these chlorides develops he pore structure to the fullest-extent. l The dry colloidalsilica (still in the'trays) is mow-washed freeof chlorides and again subjected to the-drying processfuntil thec'oL loidal" silica has; a dry external appearance. Thepores of the colloidal silica. are now full use in adsorbing moisture from a gas or liquid. The colloidal silica is removed to a sired, without loss or injury to the colloidalsilica. The colloidal silica after heating to 75091-0. now has aiwater content offlless than 2% of the'weight of the dry colloidal silica.

The less water remaining, the greater will 'be the 'adsorptive powers of-the colloidal This volume would require O.187 5Qof a poundofpum laumontite but if the rock carriesonly 25%" of laumontite then '0.75 of;a,pound of.mix-- turewould be required. The mixture of rock' silica. The colloidal silica produced by the foregoing described m'ethod is a hard, glassy,

granular'transparent, highly porous substance consistingiessentially of silica (SiO Visible through a-testtube inch in diameter. 'Small quantities were added to .the

.adsorptive materialsuntil theywere saturatedwith coloringimp'uritie's and the liquid rendered water white Results were as fol- T lowsr; I

- Considering colloidal silica as having100% efiiciency, the other materials have efficiencies ofj76%', 72%and67 respectively} Claiins-z; v. A. .m: J

1. The process of making vcolloidal silica,

,Gram s c leaned mag as a gn.

low trays," allowingitf. toistandrtherein :until' it solidifies andi causing it to dry slowly; dryin rooms or in the direct rays of the! sun. 2.3 eprocessofmakingicolloidali silica finelyground mineral laumontite with dilute or silica ge1,'whichco1nprises the mixing of hydrochloricacid,.without the application of heat, by slightlyfstirring the former into thea'latter," allowing. the mixture t o,:,settle,

decanting the supernatant solutioninto'shallowitrays, allowing itto stand therein until it solidifies,.slowly: drying the solidified contents of thev trays,:trea ting it with water to 1 dissolve andremove the chlorides which havev become crystallized therein, Ie-drying? said solidified contents of the trays, andxfinally, expellinglall butia trace vof-the water, from the j pores thereof by subjecting them to. the

a ofi 'water,theconditicn exism after action (Siam-activating ifll'naOe-qu Y Aux.

3, process of making an exceptionally porous and heat-resisting colloidal silica, or

silica gel, which comprises the stirring of 7 sun or slowly drying'it in a drying-room,

washing the crystallized chlorides out of the ores of said gel, re-drying said gel and, ally, expelling all but a trace of the water from the pores thereof by subjecting said solidified gel to, a heat of approximately 7 50. C. in a re-activating furnace.

4. The process of making colloidal silica, or silica gel, which" comprises the mixing of mineral laumontite with dilute hydrochloric acid, without the application of heat, allowingthe mixture to settle, decanting the supernatant solution, allowing it to stand after decanting until it solidifies, and then causing it to dr i In testimony whereof, we hereunto aflix our signatures.

, PERCYW. PORTER.

, JRUSSELL E. NEEDHAM. 

